Method for the acquisition of optical coherence tomography image data of retina tissue of an eye of a human subject

Abstract

In a method for the acquisition of optical coherence tomography image data of retina tissue of an eye ( 99 ) of a human subject using an acquisition device comprising an imaging optics ( 2 ), a first image associated with a baseline relative positioning of the eye ( 99 ) of the human subject with respect to the imaging optics ( 2 ) is acquired at a first point in time. The baseline relative positioning is stored. At a second point in time being different from the first point in time, the baseline relative positioning of the same eye ( 99 ) of the same human subject with respect to the imaging optics ( 2 ) is re-established and a second image is acquired. For re-establishing the positioning, a present relative positioning of the eye ( 99 ) of the human subject with respect to the imaging optics is determined based on a video image of an iris region of the eye. A corresponding device comprises an imaging optics ( 2 ), a head support to be contacted by a head portion of the human subject, the head support defining an entrance position of the sample beam entering an eye of the human subject, a camera ( 71 ) for acquiring a video image of an iris region of the eye, a display ( 75 ) for displaying a target image to the human subject, the target image indicating a direction of a line of vision to be assumed by the human subject, and a processor for determining a present relative positioning of the eye of the human subject with respect to the imaging optics, based on the video image, for comparing a present relative positioning of the eye ( 99 ) of the human subject with respect to the imaging optics ( 2 ) to a stored baseline relative positioning, for affecting the target image as long as the present relative positioning does not correspond to the stored baseline relative positioning, and for triggering the acquisition of image data when the present relative positioning corresponds to the baseline relative positioning.

The invention claimed is: 
     
       1. A method for the acquisition of optical coherence tomography image data of retina tissue of an eye of a human subject using an acquisition device comprising an imaging optics, comprising the steps of:
 a) at a first point in time acquiring a first image associated with a baseline relative positioning of the eye of the human subject with respect to the imaging optics; 
 b) storing the baseline relative positioning; 
 c) at a second point in time being different from the first point in time, re-establishing the baseline relative positioning of the same eye of the same human subject with respect to the imaging optics, and acquiring a second image, 
 where 
 d) for re-establishing the positioning, a present relative positioning of the eye of the human subject with respect to the imaging optics is determined based on a video image of an iris region of the eye, the determination comprising the step of determining a three-dimensional position and an orientation of the eye, 
 e) the re-establishing step includes displaying a target image to the human subject, the target image indicating a direction of a line of vision to be assumed by the human subject, and 
 f) a present relative positioning of the eye of the human subject with respect to the imaging optics is compared to the stored baseline relative positioning, the displayed target image is affected as long as the present relative positioning does not correspond to the stored baseline relative positioning, and the second image is acquired when the present relative positioning corresponds to the baseline relative positioning. 
 
     
     
       2. The method as recited in  claim 1 , characterized in that the re-establishing step includes an automated repositioning of the imaging optics. 
     
     
       3. The method as recited in  claim 2 , characterized in that a head of the human subject is held in a fixed position with respect to a base of the acquisition device and in that for repositioning the imaging optics is moved with respect to the base. 
     
     
       4. The method as recited in  claim 1 , characterized in that a position of a limbus cornae in the video image is determined and used as a reference for the present relative positioning of the eye. 
     
     
       5. The method as recited in  claim 1 , characterized in that the three-dimensional position and the orientation of the eye are determined by identifying the following quantities:
 a) a center of eye rotation; and 
 b) a normal vector to a limbus plane. 
 
     
     
       6. The method as recited in  claim 1 , characterized in that the determination of the present relative positioning of the eye with respect to the imaging optics comprises the step of determining a center of corneal curvature based on reflected light rays of at least two light sources illuminating the eye, the at least two light sources being spaced from each other. 
     
     
       7. The method as recited in  claim 1 , characterized by the step of determining a radius of corneal curvature of the eye of the human subject by recording video images, simultaneously acquiring OCT images of the cornea to determine a distance of the cornea from the imaging optics, assigning distance values to locations of the video image and determining the radius by a numerical optimization algorithm. 
     
     
       8. The method as recited in  claim 1 , characterized by the step of determining a distance of the center of eye rotation and a center of corneal curvature of the eye of the human subject. 
     
     
       9. A device for the acquisition of optical coherence tomography image data of retina tissue of an eye of a human subject, comprising
 a) an imaging optics; 
 b) a head support to be contacted by a head portion of the human subject, the head support defining an entrance position of the sample beam entering an eye of the human subject; 
 c) a camera for acquiring a video image of an iris region of the eye; 
 d) a display for displaying a target image to the human subject, the target image indicating a direction of a line of vision to be assumed by the human subject; 
 e) a processor for determining a present relative positioning of the eye of the human subject with respect to the imaging optics, based on the video image, the determination comprising the step of determining a three-dimensional position and an orientation of the eye, for comparing a present relative positioning of the eye of the human subject with respect to the imaging optics to a stored baseline relative positioning, for affecting the target image as long as the present relative positioning does not correspond to the stored baseline relative positioning, and for triggering the acquisition of image data when the present relative positioning corresponds to the baseline relative positioning. 
 
     
     
       10. The device as recited in  claim 9 , characterized in that the device comprises a base, the head support being fixed to the base and the imaging optics being movable with respect to the base. 
     
     
       11. The device as recited in  claim 10 , characterized by an adjustment mechanism for automatically three-dimensionally adjusting a position of the imaging optics with respect to the base.